A family study of primary affective disorders is being performed. Children at risk within these families are studied for predictors of vulnerability to adult disorders. Biologic characteristics of the patients are evaluated for usefulness as genetic markers of vulnerability to affective disorders. Among the biologic variables studied in this way are platelet monoamine oxidase activity and erythrocyte catechol-O-methyl transferase activity. Genetic linkage of affective disorders to known chromosomal markers is also studied. Mathematical models of genetic transmission are being developed for application to these data. Methodological developments are underway in assessment of diagnostic relability and in development of a data banking system for clinical research. BIBLIOGRAPHIC REFERENCES: Gershon, E.S.: Genetic and biologic studies of affective illness. In Impact of Biology on Modern Psychiatry, Gershon, E.S., Belmaker, R.H., Kety, S.S. and Rosenbaum, M. (Editors) Plenum Press, N.Y. pp. 207-228, 1977. Leckman, J.F., Gershon, E.S., Nichols, A.S. and Murphy, D.L.: Reduced platelet monoamine oxidase activity in first degree relatives of individuals with bipolar affective disorders: A preliminary report. Archives of General Psychiatry. 34:601-606, 1977.